I accepted a standard system update request this morning (8/29/18) and when the system restarted, I could no longer access both screens. I had a situation where I had only mouse access on the left screen, but apps launched on only the right screen. I have been running this basic config for two years, and have installed new images multiple times, and always accepted updates, but this one busted me. I resorted to unplugging the right-hand monitor and am now running in single screen mode.
How can I correct this?